(a) Field of the Invention
The present invention relates to a method of controlling a metallic layer etching process and a method of regenerating an etchant for the metallic layer etching process based on a near infrared (NIR) spectrometer and, more particularly, to an NIR spectrometer-based etching control method and etchant regeneration method which automatically analyzes the composition of an etchant used in the lithography process for fabricating a semiconductor device or a liquid crystal display device in real time, thereby controlling the etching process and regenerating the etchant in an accurate and effective manner while reducing the required period of time therefor.
(b) Description of the Related Art
As a large-size semiconductor device or liquid crystal display device becomes to be the choice of electronic consumers, the amount of solvents used in fabricating such a device has been significantly increased. In this situation, effective use of the solvents should be made to optimize the device fabrication process. Among such solvents, etchant is used to etch a metallic layer of chrome or aluminum, on which a photoresist layer of a predetermined pattern is formed as a mask, so that a patterned metallic layer is formed. After the etching is made, the etchant is recovered, and re-used in the next etching process. As the etchant is repeatedly used, alien materials are continuously incorporated into the etchant, and the initial composition of the etchant is continuously altered. When such an alteration degree in the initial composition exceeds the critical value, the etchant cannot be used for the etching purpose without adjusting the composition. In this case, the alien materials should be removed from the etchant, and the components of the etchant exhausted through the etching process should be newly supplied thereto. That is, the etchant should be regenerated before it is reused in the next etching process.
Meanwhile, a conventional way of determining whether the etchant can be still used for the etching purpose is to observe whether spots or stains are formed on a substrate during the etching process, thereby identifying the degree of contamination and variation in the composition of the etchant. However, with such a technique, the etchant cannot be analyzed quantitatively and suitably. That is, either the etchant to be waste-disposed may be used for the etching while causing process failure, or the etchant to be reused may be waste-disposed.
In the regeneration process of the etchant, the components of the etchant should be analyzed from time to time to regenerate the etchant of a uniform composition. For this purpose, conventionally, the user himself extracts a sample from the regenerator, and analyzes the sample with various analytical instruments. However, this method needs much time and effort for the analysis. Furthermore, when the required components determined by the time-consuming analysis are supplied to the regenerator, the regenerator is liable to be full of the etchant due to the etchant delivered from the etching process. In this case, part of the etchant should be discharged from the regenerator to supply the required components thereto. Consequently, the operation of the regenerator is discontinuously made, resulting in increased production cost and time.
Furthermore, in order to analyze various components of the etchant, separate analytic instrument should be used for each component, and the concentration of the sample should be adjusted to be suitable for each analytic instrument, and more than thirty minutes is required for the analysis. This makes it difficult to perform the desired real-time analysis.
In order to overcome such problems, it has been recently proposed that an on-line analytic equipment should be used for such an etchant analysis. However, the currently available on-line analytic equipment at best makes automatic sampling so that the desired real-time etchant analysis cannot be achieved. Furthermore, with the currently available on-line analytic equipment, collective information for treating and processing the etchant used in the lithography process cannot be obtained in real time. Therefore, there is a demand for a technique where the composition of the etchant can be analyzed in real time, and the etchant should be appropriately treated on the basis of the analysis.